Means for cooling gas turbine blades



May 9,1950

A. C. COWLES, JR

Isms FOR cbounc GAS TURBINE BLADES Filed June 30, 1945 Qwuvwkw Alba!) 0.Carlos, Jr

Patented May 9, 1950 Albon C. Cowles, In, United States Navy ApplicationJune 30, 1945, Serial No. 602,645.

(Granted under the act of March 3,'1883, as

amended April 30, 1928; 370 0. G. 757

3 Claims.

This invention relates to turbine blades or vanes, and particualrly togas turbine blades of the type in which a layer ofcool air is providedimmediately adjacent the surface normally ex: posed to the extremely hotexpanding gases prevent undue heating of those surfaces.

An object of the present invention is to 111-.

flow of cool air through the passageway 2 formed by' the spacing betweenthe shields i and 1,

crease the eiliciencyof the gas turbine engine by.

decreasing the volume of excess cool air normally required to lower thetemperature ofthe gases to which the turbine blades are exposed.

A further obj ect is toprovide gas turbine blades with a laminar flow ofgases with a layer of cool air contiguous to all parts of thelexposedblade surfaces.

A still further object of this invention is to provide a turbine bladewith one or more shields streamline in construction to enhance the freeflow of gases wherein all surfaces, including those of the streamlineshields, are. protected from the hot gases by. a layer of cool air. 1

These and other objects and advantages of the invention will be apparentfrom the following specification and taken with the accompanyingdrawing, wherein like numerals refer to like parts, inwhich: v

- Fig. 1 is a radialsection of l-i of F18. 2;

Fig. 2 is a section taken along the line 2-2 of Fig. 1;

a turbine blade and -a portion of the blade support taken along line Fi3 is a section taken along the line 3-: Fig.1;

through the passageway 8 formed by the-spacing between, the parts 6 andI of the shield I, and through the passageway alongside and over the"mainsection I of the turbine blade, as shownby the arrows. .Also, coolair will flow along the'outside surface of the shield through thepassageway ll formed by the spacing between the shield I and the framell of the turbine. The bottom portion of the shield 5 is of scoop shapedconstruction consisting of a lip or projection l2 extending in adirection of rotation of the turbine rotor, and'has a curvilinearpassageway I2 to permit a free flow of air scooped up by the lip l3through'the various aforementioned passageways. ;In order to lighten theweight of each of the-shields 5, a part of the unexposed portion of samewhich rests against the base portion 2 of the turbine blade may berecessed, as shown in Fig. 2. The shields 4 and 5 are bolted orpreferablywelded to the base portion 2 of the turbine .blade prior topositioning of the blade'on the operating gases.

the'turbinerotor so that when assembled, the' top portions oftheadjacent shields 5 form an annulus and will provide a smooth surfaceto The flow of air through and around the shields and the turbine bladeis shown in the drawings, by the arrows thereon. As can be seen, all theexposed surfaces, and especially the surface of the main section ofblade I, will be protected by a layer of cool air. Because of Fig. 4 isa radial section through another cmbodiment showing a single streamlineshield; and

Fig. 5 is a section taken along line 5 -5 .of

I"! .4. is shown'by Figs. 1 and 3 inclusive, the nu meral l refers to amain section of a turbine blade' having a base portion 2 which is fittedtightly into an opening in the periphery of a turbine wheel 3 so as tobe wedged securely therein in a manner well known in the art. Aplurality of shields l and 5, spaced apart to form a passageway 9 andstreamlined in construction so as not to affect the normal flow of thehot expanding gases nor to reduce the reactive forces of these gases,are welded or otherwise secured to the base portion 2 to forma unitaryconstruction. The shield 4 consists of two parts, 6 and I, spaced fromeach other to form a passageway 8,

overlapping at their end portions and being joined along their trailingedges and spaced from the main section I of the turbine blade along bothsides of same. This construction permits the free a a Each shield 20 iswelded at its lowermost portion at its trailing edge to the side wall ofthebase 2 of the turbine blade, or bolted thereto as the'streamlinedshape of the shields l and I, there will be a smooth and even flowof'cool air which will have little tendency to mix with the hot ex,-panding gases, but will instead form a protective layer of cool air.

Figs. 4 and 5, which show a modification of the invention, include onlya single streamline shield 20, constructed as anannulus so that each ofthe turbine blades is provided with a shield.

shown, to form the air passageway 2 I. The trailing edge of the shield20 above the base 2 of the turbine blade is spaced therefrom'to formpas-- 'sageways. for cooling air.

turbine is spaced from the shield 20 to form another air passageway 22.In this modification,

' all of the turbine blades are first assembled-onto the rotor wheel andthe annulus carrying the shields 20 bolted or welded thereon. Cool airflows then through the passageway 22 to provide the outer surface of theshield 20 with a layer The frame 22 of theor coolair, and also-throughthe passageway in.

alongside and, over the main section I of the turbine blade tocompletely envelope the same- Wifll laminar flow of cool air. 1Asindicated by the arrows shown in mg drawing, a relatively small volumeof airis permitted to flow to the base of the turbine blade and divertedthrough a plurality of passageways formed by thestreamlined shields. Thevarious exposed surfaces are maintained at a temperature lowertha'n'that of the not operating gases by; the layer of cool air flowingalong the exposed surfaces.-

This results in a marked increase in the efliciency inthe performance ofthe turbine and a drop in the percentage of failuresof' turbine bladesdue 2. In: a turbine blade air-cooling means, a pinrality of streamlinedoverlappingshields extending outwardly from the base of each blade,following substantially the contour around the forwardedge of said-bladeor of .the inner portion of an overlapped shield, and closelyapproaching said blade or'said portion at their outer edges todistribute cooling air' supplied at the base of the blades in a laminarfashion over the surfaces of said blade and said overlapped shields, andmeans for directing cooling air from said air supplied at the base overthe innermost shield.

to warping and breaking causedby the intense heat of those gases. Sincetheloperating gases are hottest at the primary stages and decrease intemperature in the succeeding stages. the passageways formed by theshields on the blades of the primary stages may be large and 'maydecrease in size inthe succeeding stages. I While the forms'of mechanismherein shown 4 3. A turbine blade construction comprising a turbineblade, a base therefor adapted to be fitted into a turbine wheel and anopen-ended shield overlying the forward portion of saidblade in spacedrelation thereto and mounted on said base for distributing cooling airsupplied at I the .base of the blade in a laminar flow over the anddescribed constitute the preferred forms of embodiment of the presentinvention, it is understood that other forms might be adopted, allcoming within the scope of the claims which follow. Theinventiondescribed herein may be manufactured and used by or for theGovernment of the United States of' America for governmental purposeswithout the thereon or therefor.

What I claim is: 1

. 1. In a turbine blade air-cooling means, a plurality of streamlinedoverlapping shields extendpayment of any royalties ing outwardly'fromthe base of each blade, following substantially the contour around theforward edge of. said blade or of the inner portion of an overlappedshield, and closely approaching said blade or said portion at theirouter edges to distribute cooling air supplied at thebase of the bladesina laminar fashion over thelsurfaces of said bladeand said overlappedshields.

surface of said blade, said open-ended shield being a substantiallyU-shaped member having two sections spaced from each other,-overlappingat .end

portions and being Joined along'their trailingj edges. v v

os 'q.'cowLE's.-Ja

I l Remittances-"siren I The following. references are of record in thefile of this patent:

Germany Jan 5, 1922

